In humans, melanin is the primary determinant of skin color. In the skin, specialized cells found in the basal layer of the dermis called melanocytes, produce melanin. Human possess similar concentrations of melanocytes in their skin, but present different concentrations of skin melanin based on their ethnicity.
Melanin plays an important biological role as a photoprotectant because it absorbs harmful UV radiation and transforms that energy into harmless heat. This property enables melanin to dissipate more than 99.9% of the absorbed UV radiation as heat. Melanogenesis, or increased production of melanin in human skin, is stimulated by UVB-radiation to produce what is commonly known as a tan. Although a tan appearance is desired by some people in various cultures, some cultures desire a lighter skin appearance. Further, melanin pigment disorders are perceived as cosmetic flaws. Examples of these local hyperpigmentations would be: freckles, melasma, chloasma, post-inflammatory hyperpigmentation, liver spots and many more. It is common to all forms of hyperpigmentation that a disturbance in the melanogenesis arises.
Various strategies have therefore been developed to reduce the pigmentation of the skin. One of the most often used skin and hair lighteners is hydroquinone or the hydroquinone glycoside of arbutin. However, these compounds have a cytotoxic effect on melanocytes and have an irritative effect on the skin. Another option is the inhibition of the synthesis of melanin by inhibiting the pacemaker enzyme tyrosinase. For this, the substances kojic acid and derivatives of kojic acid such as e.g. kojic acid dipalmitate kojic acid, azelaic acid, oxyresveratrol, linolenic acid, vitamin C and derivatives of ascorbic acid such as, for example, ascorbyl phosphate or ascorbyl palmitate, inter alia, are used. However, these substances have a high sensitizing potential, cause contact allergies, exhibit inadequate chemical stability in cosmetic formulations, or have only an unsatisfactory effect on the skin.
Moreover, strategies are also known which prevent the transfer of the melanin from the melanocytes into the surrounding keratinocytes. Thus, protease inhibitors are described which inhibit the PAR2 receptor on the surface of the keratinocytes and as a result reduce the transfer of the melanin. Hydrolysates from soya beans and niacinamide are said to reduce pigmentation in this way.
Increased renewal of the skin is also described for lightening the skin. For this procedure, alpha-hydroxy acids such as lactic acid and glycolic acid, inter alia, are used. By means of this treatment, the uppermost skin layers are corroded away and the melanin-containing corneocytes are abraded. A disadvantage of this method is frequent irritation of the skin.
There is thus an increasing need for new, further and improved compositions for decreasing melanin production in the skin and for treatment of hyperpigmentation. There is also a long-felt need for compositions which cosmetic lightening relatively large areas of pigmented skin.
The inventors are credited with creating a canola extract with high levels of phenolic acid that satisfies these long-felt commercial needs. It was an object of the invention to provide a care active ingredient which has a skin-lightening effect, which is well tolerated.